The following meanings for the abbreviations used in this specification apply:
BS Base Station
CRN Cognitive Radio Network
HO Hand Over
KPI Key Performance Parameter
MME Mobility Management Entity
MORAN Multi Operator Radio Access Network
MOCN Multi Operator Core Network
OAM Operation And Maintenance
RAN Radio Access Network
RAT Radio Access Technology
UE User Equipment
Embodiments of the present invention relate to base stations (Macro, Pico and Femto) which form a cognitive radio network (CRN).
In mobile networks spectrum utilization and allocation is performed via static configurations based on network planning data of a Mobile Network Operator MNO. With introduction of cognitive radio methods it is not longer possible to stay with these static configurations. Moreover the principle of ‘my spectrum—my usage’ will not hold any longer. In other words Dynamic Spectrum Allocation (DSA) will lead to a paradigm change in mobile communication industry. Spectrum is not longer exclusively assigned to a single operator but jointly used by several operators with the obligation to use it collectively under fair conditions.
Today a specific spectrum block in a predefined area (e.g. region or country) is typically owned by a Mobile Network Operator. When operators share their spectrum blocks with other operators to form a joint cognitive radio network it is necessary to define a policy which exactly defines the rules how the spectrum is assigned to and released by each operator. The basic principle of such a policy is shown in FIG. 2. Operator A owns spectrum a and Operator B owns spectrum b. The spectrum is released when there is no need for it in the cell (left part of FIG. 2) and the spectrum is expanded when it is needed, e.g. users enters the cell (right part of FIG. 2). Even more complex policies follow this basic principle.
The advantage of forming a joint cognitive radio network is that each Operator is not longer bound to the owned spectrum only, i.e. Operator A uses spectrum x and Operator B uses spectrum y but both Operators are allowed to use spectrum x as well as spectrum y when it is available for usage in a specific area. Therefore, Spectrum Sharing in an defined area leads to a higher spectrum efficiency than the traditional dedicated assignment of spectrum. It is obvious that after a while spectrum x and spectrum y will mix up in Operator Network A and B. The situation will become even worse when Operators A and B offer several spectrum blocks for the common usage or further Operators (e.g. Operator C, D, . . . ) with or without adding owned spectrum are joining. Further the fragmentation of the spectrum increases with finer granularity of the defined spectrum blocks.
The fragmentation of the spectrum used by an Operator issues a lot of disadvantages. An example is shown in FIG. 3. There is an area which consists of 3 Base Stations BS (left and right belongs to Operator A while the BS in the middle belongs to Operator B). The spectrum a from Operator A and the spectrum b from Operator B is defined as a shared spectrum and can be used by both Operators according to agreed policy rules. During Operation it may happen the spectrum a and b is used by the left and right BS of Operator A while Operator B doesn't need spectrum. Without coordination between the left and right BS the left BS may decide at a time to release Spectrum block a while the right BS decides at the same or another time to release spectrum block b. When the middle BS of Operator B requests additional spectrum there is no spectrum left for the area because spectrum a and spectrum b is blocked for this area, i.e. both spectrum blocks cannot be used without interfering either the left or the right BS of Operator A.
In general spectrum sharing increases while spectrum fragmentation decreases the spectrum efficiency within an area, i.e. in a spectrum sharing scenario it is necessary to find a solution which at least limits spectrum fragmentation to get best spectrum efficiency.
Another drawback is given by the requested mobility in mobile radio networks which is based upon HOs between neighbouring cells of the RAN. A fragmentation of the cells will lead to a change in basic parameters e.g. carrier frequency and/or bandwidth between neighbouring base stations of the same operator. Therefore, fragmentation will lead to an ‘expensive’ handover between different carriers or even RATs which should be avoided. In particular required measurements of the mobile on additional frequency carriers could be avoided. Keeping the spectrum allocation between neighbouring cells almost identical allows to base the HO in a cognitive network on a ‘classical’ and efficient intra carrier intra RAT HO.
Current definitions in 3GPP allow to share Radio Networks between Operators (e.g. MORAN, MOCN, Roaming) but none of this existing concepts deal with spectrum sharing. Either an Operator owned spectrum is shared with other Operators (Roaming and MOCN) or the Radio Base Station supports multiple Operators with dedicated spectrum for each Operator (MORAN).
Moreover, current definitions in IEEE and ITU-T don't provide detailed mechanisms on spectrum sharing among operators. In particular no scheme is defined or supported which avoids the fragmentation of spectrum during the spectrum release and expansion process.